As scientists unveil artificial organs and prosthetics to improve the function of our hearts, kidneys, hands, and even eyes, it's easy to gloss over these devices' Achilles' heel: power.

The fuel cell in dialysis tubing before and after implantation in a rat.
PLoS ONE

Even building devices that run on very low power, such as pacemakers, tend to require additional invasive surgeries just to replace their batteries. Meanwhile, artificial limbs can be huge energy hogs, with the power source needing to be swapped out as frequently as every few weeks. Impractical is an understatement.

Biofuel cells could very well solve this problem. Researchers around the world are investigating how to use a body's own energy to power various devices, and one team out of France last year successfully implanted in a rat a biofuel cell that uses glucose and oxygen to generate electricity.

The cell is made of two electrodes--one that removes electrons from glucose, and another that pushes electrons to oxygen and hydrogen molecules to produce water. If these electrodes are connected to a circuit and submerged in a solution containing glucose and oxygen, the resulting flow of electrons from glucose to oxygen results in an electrical current.

Much of the recent research into biofuel cells to produce electricity has been fueled by the increased availability of carbon nanotubes, which are extremely efficient electrical conductors. "In the last 10 years there has been an exponential increase in research, and some important breakthroughs in enzyme research," Serge Cosnier of the French team told the BBC.

The idea of powering fuel cells using glucose and oxygen dates back to the '70s, but energy production was too low to get anyone terribly excited. Cosnier now estimates that, by improving efficiencies in electron-donating enzymes, these cells could produce 50 times the energy they were able to obtain during their three-month experiment with the rat.

His team plans its next test on cows, which, being far larger than rats, should produce more electricity--ideally enough to power a transmitter that relays information about the device and control sensors inside the animal.

About the author

Elizabeth Armstrong Moore is based in Portland, Oregon, and has written for Wired, The Christian Science Monitor, and public radio. Her semi-obscure hobbies include climbing, billiards, board games that take up a lot of space, and piano.
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